import java.util.Scanner;

public class Main4 {

    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNextInt()){
            int n = scanner.nextInt();
            System.out.println(firstDouble(n));
        }
    }

    private static int firstDouble(int n){
        int[][] arr = new int[n][2*n-1];
        arr[0][0] = 1;
        for(int i = 1; i<n;i++){
            for(int j =0 ;j < (2*i+1);j++){
                arr[i][j] = mySum(arr[i-1],j);
            }
        }
        for(int j =0 ;j <(2*n);j++){
            if(arr[n-1][j]%2==0){
                return j+1;
            }
        }
        return -1;
    }

    private static int mySum(int[] arr,int j){
        int num = 0;
        if(j-2>=0){
            num+=arr[j-2];
        }
        if(j-1>=0){
            num+=arr[j-1];
        }
        num+=arr[j];
        return num;
    }
}